1. Field of the Invention
The present invention relates to a lithium rechargeable battery. In particular, the present invention relates to a lithium rechargeable battery in which an anti-rotation groove is integrally formed with a lower recess of a safety vent at a lower surface of a cap plate. In addition, an insulating plate and a terminal plate rest in the anti-rotation groove so that the terminal plate is prevented from rotating when a cap assembly is assembled. The present invention also relates to a lithium rechargeable battery, in which a resting recess is formed on a lower surface of a cap plate, and an insulating plate and a terminal plate rest in the resting recess so that the terminal plate can be prevented from rotating when a cap assembly is assembled.
2. Description of the Background
Recently, portable wireless devices such as video cameras, portable phones, and portable computers that are compact and lightweight and are equipped with various functions have been developed. Studies have been actively performed on rechargeable batteries that are used as power sources for the portable wireless devices. For example, the rechargeable batteries include Ni-Cd batteries, Ni-MH batteries, Ni-Zn batteries and lithium rechargeable batteries.
Lithium rechargeable batteries may be fabricated in a compact size and have a high operating voltage and high energy density per unit weight, which makes them suitable for use in the advanced electronic technology fields.
FIG. 1a is an exploded perspective view of a conventional lithium rechargeable battery and FIG. 1b is a sectional view of a cap plate included in the conventional lithium rechargeable battery.
The lithium rechargeable battery may be obtained by accommodating an electrode assembly 112 including a second electrode plate 113, a first electrode plate 115 and a separator 114 in a can 110 together with an electrolyte, and then sealing an upper opening 110a of the can 110 using a cap assembly 120. In general, the first electrode plate 115 may be a negative electrode plate and the second electrode plate 113 may be a positive electrode plate.
The cap assembly 120 includes a cap plate 140, an insulating plate 150, a terminal plate 160 and an electrode terminal 130. The cap assembly 120 is housed in an insulating case 170 and assembled with the upper opening 110a of the can 110, thereby sealing the can 110.
The cap plate 140 comprises a metal plate with a size and a shape that corresponds to the upper opening 110a of the can 110. The cap plate 140 is positioned towards the top of the cap assembly 120 with a first terminal hole 141 that has a predetermined size and the electrode terminal 130 is inserted into the first terminal hole 141. When the electrode terminal 130 is inserted into the first terminal hole 141, a gasket tube 149 is provided around the electrode terminal 130 to insulate the electrode terminal 130 from the cap plate 140. A safety vent 146 is formed at one side of the cap plate 140 and an electrolyte injection hole 142 with a predetermined size is formed at the other side of the cap plate 140. After the cap assembly 120 has been assembled with the upper opening 110a of the can, the electrolyte is injected into the can 110 through the electrolyte injection hole 142. Then, the electrolyte injection hole 142 is sealed with a plug 143.
Referring to FIG. 1b, the safety vent 146 includes an upper recess 148 formed on an upper surface of the cap plate 140 and a lower recess 147 formed on a lower surface of the cap plate 140. The safety vent 146 breaks when the internal pressure of the rechargeable battery increases due to over-charge, over-discharge, or overheating of the rechargeable battery so that gas contained in the rechargeable battery can be exhausted to the exterior through the safety vent 146, thereby preventing explosion of the rechargeable battery. The position of the safety vent 146 in the rechargeable battery may vary depending on the type of battery.
The electrode terminal 130 is coupled with a first electrode tab 117 of the first electrode plate 115 or a second electrode tab 116 of the second electrode plate 113 so that the electrode terminal 130 may serve as a negative electrode terminal or a positive electrode terminal.
The insulating plate 150 may comprise substantially the same insulating material as the gasket and is coupled with the lower surface of the cap plate 140. The insulating plate 150 is formed with a second terminal hole 151, which is aligned with the first terminal hole 141 of the cap plate 140 and into which the electrode terminal 130 is inserted. The insulating plate 150 is positioned on the lower surface of the cap plate 140 with a resting recess 152 with a size and a shape that corresponds to the terminal plate 160 such that the terminal plate 160 may rest in the resting recess 152.
The terminal plate 160 may comprise a Ni alloy and is coupled with the lower surface of the insulating plate 150. The terminal plate 160 is formed with a third terminal hole 161, which is aligned with the first terminal hole 141 of the cap plate 140 and into which the electrode terminal 130 is inserted. Since the electrode terminal 130 inserted into the first terminal hole 141 of the cap plate 140 is insulated from the terminal plate 140 by the gasket tube 149, the terminal plate 160 may be electrically connected to the electrode terminal 130 while being electrically insulated from the cap plate 140.
In order to couple the electrode terminal 130 with the cap plate 140, the insulating plate 150, and the terminal plate 160, the electrode terminal 130 is inserted into the first terminal hole 141 of the cap plate 140 by applying predetermined pressure and rotational force to the electrode terminal 130. Thus, the electrode terminal 130 is coupled with the terminal plate 160 by passing through the first, second and third terminal holes 141, 151 and 161, respectively. Thus, the insulating plate 150 and the terminal plate 160 may rotate about the first terminal hole 141 of the cap plate 140 while the electrode terminal 130 is being inserted into the first, second and third terminal holes 141, 151 and 161, so the insulating plate 150 may be offset from the terminal plate 160.
In addition, when the positive electrode tab 116 is coupled with the lower surface of the terminal plate 160, the terminal plate 160 may rotate so that the terminal plate 160 may be offset from its initial position.
Furthermore, when a lead plate (not shown) connected to a protective circuit module is coupled with the electrode terminal 130 after the cap assembly 120 has been assembled, the terminal plate 160 may rotate together with the electrode terminal 130 so that the terminal plate 160 may be damaged.
In addition, in order to couple the cap assembly 120 with the insulating case 170, the insulating plate 150 and the terminal plate 160 must be reverse-rotated about the electrode terminal 130 such that they are aligned in the same direction as the cap plate 140. However, such a process not only lengthens the process time, but also causes deformation of the terminal plate 160 made from a thin metal plate.